First investigation on the applicability of an active noise control system on a tracked tractor without cab

In last years, several research teams pointed their attention on the application of active noise control systems (ANC) inside the cabs of agricultural tractor, with the purpose of reducing the driver exposition to noise, that is only partially controlled by the frame of the cab. This paper reports the results of a first experience that aimed at verifying the applicability of an ANC on a medium-high power, tracked tractor without cab. The tested tractor was a Fiat Allis 150 A, equipped with rear power take off, used in the execution of deep primary tillage in compact soils. It is a tracked tractor without cab, with maximum power of 108.8 kW at 1840 min–1 of the engine. The ANC consists of a control unit box based on a digital signal processor (DPS), two microphones, two speakers and a power amplifier. The instrumentation used in noise data collecting and processing consisted of a multichannel signal analyzer (Sinus - Soundbook), a ½” microphone capsule and an acoustic calibrator, both Bruel & Kjaer. The study aimed at evaluating the behaviour of the ANC by means of tests carried out under repeatable conditions, characterized by pre-defined engine speed values. Three replications have been made for each engine speed. The sampling time was 30 s. Two series of tests were performed in order to compare the results observed with the ANC on and off. The engine speed adopted in the study ranged from 600 min– 1, up to 2000 min–1 (maximum speed) with steps of 100 min–1. The ANC proved to be effective in the interval of speed between 1400 and 1700 min–1, where the samplings have been intensified, adopting steps of 50 min–1. In such an interval, the attenuation observed with the ANC system on appeared evident both as weighed A sound pressure level (from 1.29 up to 2.46 dB(A)) and linear (from 4.54 up to 8.53 dB). The best performance has been observed at the engine speed of 1550 min–1, with attenuations, respectively of 2.46 dB(A) and 7.67 dB. Outside of the engine speed interval 1400 - 1700 min–1, the attenuations always resulted lower than 1 dB(A) for the weighed A sound pressure level and between 0.66 and 7.72 dB

MicroRNA expression is associated with auditory dysfunction in workers exposed to ototoxic solvents and noise

This study is part of a project on early hearing dysfunction induced by combined exposure to volatile organic compounds (VOCs) and noise in occupational settings. In a previous study, 56 microRNAs were found differentially expressed in exposed workers compared to controls. Here, we analyze the statistical association of microRNA expression with audiometric hearing level (HL) and distortion product otoacoustic emission (DPOAE) level in that subset of differentially expressed microRNAs. The highest negative correlations were found; for HL, with miR-195-5p and miR-122-5p, and, for DPOAEs, with miR-92b-5p and miR-206. The homozygous (mut) and heterozygous (het) variants of the gene hOGG1 were found disadvantaged with respect to the wild-type (wt), as regards the risk of hearing impairment due to exposure to VOCs. An unsupervised artificial neural network (auto contractive map) was also used to detect and show, using graph analysis, the hidden connections between the explored variables. These findings may contribute to the formulation of mechanistic hypotheses about hearing damage due to co-exposure to noise and ototoxic solvents

Miniaturized P-V probes make possible new knowledge on otoacoustic emissions generation mechanism and ear canal input impedance

In this work an innovative methodology for measurement and analysis of Otoacoustic Emissions (OAEs) will be shown. Nowadays noninvasive measurements of OAEs are yielded in the acoustic pressure field only. We realized a device that directly plugs into the human ear canal and can also measure the OAE velocity field. Such a device is equipped with a very small intensity probe com-posed of a micro anemometer MEMS coupled to a sensitive miniature microphone. In this way p-v measurements can be carried out at the same time, providing further information about the mechanisms of OAEs generation, as well as allowing an accurate measurement of input impedance of the ear canal. In this case the p-v measurements of OAEs are best realized on Distortion Product OAEs (DPOAEs), these emissions being more easily measured with our technique. The developed system uses an intensity probe carried out by Microflown and coupled to a dedicated electronic front-end. A high resolution acquisition system is provided by National Instruments and driven by a suitable software developed in LabView platform. This software operates on data recorded in real time and performs a customized analysis of the recorded signals. The results thus obtained, in particular those related to the measurement of the input impedance of the acoustic system, are compared with those already obtained by other indirect methods available in literature

A New Synthetic Polymer as a Support for Enzyme Immobilization

A method for the preparation and derivatization of an acrylic polymeric support and some topochemical reactions are described here. The support was also found to be effective to immobilize enzymes

Intensimetric detection of distortion product otoacoustic emissions with ear canal calibration

Distortion product otoacoustic emissions (DPOAEs) have been accurately measured with an intensimetric technique, involving simultaneous measure of pressure and velocity in the ear canal, which allows one to correctly calibrate both the input stimuli and the otoacoustic emission (OAE) level. Suitable combinations of standard intensimetric quantities, active intensity and power density [Stanzial, Shiffrer, and Sacchi, J. Acoust. Soc. Am. 131, 269-280 (2012)], are used to equalize the stimuli transmitted to the middle ear, and to estimate the DPOAE level emitted by the eardrum. The DPOAE intensimetric spectra are consistent with those recorded with a high-quality conventional otoacoustic probe with state-of-the-art calibration of both stimulus and OAE response [Charaziak and Shera, J. Acoust. Soc. Am. 141, 515-525 (2017)], demonstrating the applicability of the intensimetric method to OAE measurements